The present invention relates to an improved auger for drilling into the earth.
The mechanical advantage of the lever has been utilized in augers for drilling for centuries. Typically, an auger drill rod that is rotated in a clockwise manner has affixed to it a flight with its helix also oriented in the clockwise or right hand direction. While the drill stem is rotated constantly in a clockwise manner, the helical flighting on such an auger lifts tailings away from the drill bit and tends to bring them to the surface as the auger is pulled down into the earth.
When drilling bore holes for seismic exploration or when drilling deeper holes, a drill string is conventionally used, made up of a plurality of lengths of drill steel which is usually hollow along its length. In auger drilling, the flight is spirally wound and secured to the exterior cylindrical surface of the drill steel. Water and drilling muds are forced under pressure downwardly through the drill string to the drill bit secured to the down hole end of the lower most drill steel so as to lubricate and cool the drill bit and help carry the tailings upwardly to the surface.
Auger drilling is recognized as comparatively fast. However, because of the very nature of the standard auger, the depth to which it can be utilized in drilling is limited.
The flighting of the auger is designed to lift the tailings and water mixture produced at the bit away from the bit and up to the surface.
As the hole gets deeper, the weight of the tailings being lifted decreases the torque that is able to be delivered at the drill bit. There is the increasing possibility in this instance that the material being lifted will clog the auger or that the bore hole wall may collapse around the auger. If a standard auger is rotated in a clockwise direction when trapped in a hole, it will only pull itself deeper into the bore hole. Reversing the direction of the rotation, on the other hand, will only disconnect the lengths of drill steel above the trapped length(s) of drill steel.
The only alternative of lifting the auger for cleaning becomes progressively more difficult as the hole becomes deeper. Auger drilling therefore has been limited to use in shallow depths such as required for seismic exploration and post holes for construction.
A reverse action auger has been described and illustrated in U.S. Pat. No. 4,484,642 of Evans issued Nov. 27, 1984. In this case, the auger is rotated as well in a clockwise manner but it has affixed to it a flight with its helix oriented in the left hand counterclockwise direction. Theoretically, the operation of such an auger creates a back (down hole) pressure that forces the tailings and mud created by the drill bit into the natural fissures, cracks or porous zones of the surrounding earth, so that nothing reaches the surface. Such a reverse action auger appears to work well when drilling in certain porous materials as are encountered in shallow seismic holes although the restraining of the flow of tailings away from the bit does result in excessive wear on the bit. When drilling in consolidated materials however, there is very seldom any place for tailings and water to go but up to the surface. In this instance, the continuous reverse action auger is a serious hindrance in that it continually forces material down the hole while the bit is producing more tailings. The deeper the hole, the more serious the problem. As well, with no upward movement of water and in fact a downward movement of the flighted auger all the way from the surface, a self-imposed jamming of the drill stem with dry material above the drill bit may result. This is especially hazardous in deep holes.
For drilling deep holes or drilling in materials where an auger would have difficulty because of the potential of bore hole wall collapse e.g. in sandy or very soft soils), conventional rotary drilling, as it is called, utilizes a smooth stem drill rod that is usually not much smaller in diameter than the drill bit that precedes its descent into the bore hole. The tailings or cuttings are brought to the surface by the action of the water and special drilling muds that are forced under pressure through the drill stem to both cool and lubricate the bit and then mix with the tailings. The drill bit is rotated at different speeds depending on the material being drilled. It is not unusual when drilling with this system, in certain difficult circumstances, to force casing slightly larger than the bit down the hole behind the drill bit, thus casing the hole as it is drilled and preventing bore hole wall collapse.
Traditionally, therefore, auger drilling, although recognized as a faster method of drilling, has been limited to shallow holes whereas conventional rotary drilling, although able to drill deeper, is a slower method of drilling.
Other patents of general background interest, relating to the present invention, are Canadian Pat. No. 659,104 of Sokjer-Petersen issued Mar. 12, 1963, British Pat. No. 2,132,667 of Shekisan Kogyo Co. Ltd., British Pat. No. 2,137,678 of Kabushiki Kaisha Matsuzawa Kiko, and British Pat. No. 2,132,668 of Shekisan Kogyo Co. Ltd..
It is an object of the present invention to provide an auger which overcomes the drawbacks associated with both auger drilling and conventional rotary drilling, thus enabling a system incorporating such new auger to be able drill quickly holes of any conventional size to any conventional depth. It is a further object of the present invention to provide such an auger which is not dependent, for its ability to operate, on the porosity of the walls of the drill hole. It is a further object of the present invention to provide an auger which will reduce the tendency of bore hole walls to collapse while at the same time reducing the amount of drilling muds needed when compared to traditional drilling systems.